PUBIC HEALTH ASSESSMENT
TRW MICROWAVE, INC.
SUNNYVALE, SANTA CLARA COUNTY, CALIFORNIA
The TRW Microwave, Inc. Building 825 site, located in Sunnyvale, Santa Clara County, California, was formally listed on the National Priorities List by the U.S. Environmental Protection Agency in February, 1990. The California Regional Water Quality Control Board is the lead governmental agency overseeing the cleanup at the TRW site. The manufacturing facility is currently operated by FEI Microwave, Inc. At least one of several underground storage tanks apparently leaked volatile organic compounds (VOCs) into the subsurface soils and groundwater. These underground tanks and most of the surrounding contaminated soil have been excavated and removed from the site. Various variable organic contaminants (VOCs) have been detected in on-site and off-site groundwater at levels of human health concern. However, the contaminated groundwater is not a source of drinking water. On-site groundwater extraction and treatment systems have been in operation since 1985; the off-site system began operating in 1986.
The only completed human exposure pathway is from inhalation by off-site residents of volatile organic compounds migrating into homes from shallow groundwater. This pathway was originally proposed based on extrapolations from groundwater concentrations to soil-gas vapors and from soil-gas vapors to indoor air concentrations using mathematical models. Studies conducted by the California Department of Health Services indicate that the contaminated groundwater may contribute to the indoor air quality but not at a level of public health concern.
The current exposure pathway of inhalation of VOC vapors from the off-site groundwater plume is the issue that raises the most community health concerns.
Based on information reviewed, the Agency for Toxic Substance and Disease Registry (ATSDR) and the California Department of Health Services (CDHS) have concluded that this site is not an apparent public health hazard.
ATSDR's Health Activities Recommendation Panel (HARP) evaluated the data and information in the TRW Microwave Public Health Assessment for follow-up health activities. HARP determined that although exposure to site contaminants may have occurred in the past and may be occurring now, environmental sampling data were not available to assess the magnitude and public health significance of the exposure. Community health education activities, however, are ongoing and will continue to address specific community health concerns as they arise. When data become available, ATSDR and CDHS will reevaluate this site for any indicated follow-up health activities.
Since the time HARP made those determinations, environmental sampling data became available to assess exposures and that data were evaluated. The levels of site-related VOCs that may be contributing to indoor air levels are not at levels of public health concern.
The Public Health Action Plan (PHAP) for the TRW Microwave site contains a description of actions to be taken by ATSDR and/or CDHS at and in the vicinity of the site subsequent to the completion of this public health assessment. The purpose of the PHAP is to ensure that this health assessment not only identifies public health hazards, but provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. The public health actions that were to be implemented by ATSDR or CDHS, or other agencies, and the status of those actions, are as follows:
- In the areas of known groundwater contamination, implement institutional controls to prevent future use of contaminated aquifers for drinking water supplies until remediation has reduced contaminant concentrations to below levels of health concern.
- Continue flux chamber measurements of VOC soil vapor release until the value of this data is determined.
- Request the Air and Industrial Hygiene Laboratory (AIHL) of CDHS to conduct indoor air sampling at the San Miguel School. Since commercial products found in homes contain some of these organic contaminants, school sampling may pose fewer problems as compared to residential homes in terms of "background" inventory.
- When flux chamber monitoring data and indoor air data is obtained, CDHS and RWQCB should then reevaluate the significance of the potential indoor air exposure.
- Interpret and share results of indoor air sampling with concerned community.
- Continue to pursue the relevant Tumor Registry and Birth Defects Monitoring data.
As part of the agreed clean-up remedy (called the Record of Decision or ROD) each company, including TRW, will be placing a deed restriction on their own property (36). This restriction does address future well construction on that property. Apparently, no agency has the statutorial power to implement well-construction restrictions on the privately owned off-site properties.
As directed in the ROD, the companies have conducted flux chamber measurements twice a year for the last two years (36). The need for this monitoring is being reevaluated by U.S. EPA and RWQCB.
On August 20, 1991, the Health Investigation Branch within CDHS requested that AIHL conduct air sampling at San Miguel School and a control school for comparison. AIHL conducted indoor air sampling in San Miguel School and a control school, Cherry Chase School, in February 1992. Due to sampling problems, the sampling was later repeated by the Bay Area Air Quality Management District in November 1992.
The levels of the chemicals found inside the school are considered typical for indoor air. Levels that are considered typical for indoor air are based on studies of indoor air quality done throughout the United States and Europe. It is now recognized that typical indoor air quality is not particularly healthy and could cause minor symptoms. However, the levels of VOCs found inside San Miguel School are not above typical levels and should not cause health problems.
The RWQCB project manager for this site participated on the advisory committee for the indoor air sampling. Additionally, RWQCB is interested in better understanding this potential pathway. Based on the air sampling study results, CDHS does not believe that this pathway poses a public health hazard.
CDHS/ATSDR staff initiated the formation of a community-based advisory committee to oversee the workplans and interpretations of the school air sampling.
The advisory committee included seven members of the community. CDHS presented the results of the AIHL air sampling at a community meeting in August 1992. The impact of the sampling problems was discussed with the community and CDHS promised to pursue a better resolution. The results of the Bay Area Quality Management District (BAAQMD) air sampling carried out in November 1992 were presented in a fact sheet delivered by hand to the San Miguel neighborhood and in this revision of the public health assessment.
CDHS/ATSDR is no longer pursuing these data. The low level of chemical exposure that might arise from this site's contamination does not warrant the using such data.
The California Department of Health Services (CDHS) has prepared this public health assessment under cooperative agreement with the U.S. Agency for Toxic Substances and Disease Registry (ATSDR). The CDHS/ATSDR Public Health Assessment is a mechanism to provide the community with information on the public health implications of specific hazardous waste sites and to identify those populations for which further health actions or studies are indicated. The public health assessment of TRW Microwave, Inc. Building 825 (TRW) is based on a review of the Remedial Investigation (1) and Baseline Public Health Evaluation (2) in conjunction with a site visit and consultation with staff from the California Regional Water Quality Control Board (RWQCB). The public health assessment that wasreleased for public comment in January 1992, served to update the ATSDR Preliminary Public Health Assessment for TRW (3), completed by ATSDR in August 1990. This report is a revised version of the January 1992 report. As a result of the findings of the indoor air sampling study, the conclusion category has been changed from indeterminate public health hazard to no apparent public health hazard. This report has also been updated according to ATSDR's current format guidelines (4).
In 1982, it was discovered that a leaking underground solvent storage tank had contaminated soil and groundwater at the semiconductor manufacturing facility (Figure 1) originally owned and operated by TRW, Inc. (TRW)(1). At about the same time neighboring facilities, Advanced Micro Devices, Inc., at 901 and 902 Thompson Place (AMD 901/902), and Signetics Corporation, were also discovering similar contamination problems (1). The U.S. Environmental Protection Agency (U.S. EPA) nominated all three facilities to the National Priorities List (NPL). Each of these facilities has its own source of pollution, but the off-site groundwater pollution areas have merged, and the companies are being treated as one unit. RWQCB, San Francisco Bay Region (Region 2), is the lead agency overseeing the AMD 901/902/Signetics/TRW cleanup under a formal agreement with the U.S. EPA. The U.S. EPA never listed the Signetics facility on the NPL and is regulating the cleanup of the site under the Resource Conservation and Recovery Act. Therefore, this NPL-site public health assessment is evaluating the impact of the TRW contamination, which by necessity includes the commingled plume (the off-site contamination) that the AMD 901/902 and Signetics facilities are also believed to have impacted.
The site is located in the northern Santa Clara Valley city of Sunnyvale, at the southern end of San Francisco Bay (Figure 1). The area is heavily populated with commercial, light industrial and residential facilities. A 3-story building located at 825 Stewart Drive is the main structure on the site. TRW occupied the building from 1974 to 1987, fabricating and plating semiconductors. Prior to that, Aerotech occupied the three-story building, assembling and testing microwave components. The property was purchased by Tech Facility 1, Inc. in 1987. Some assets at this site were acquired by FEI Microwave, Inc. in July 1987. Currently FEI Microwave, Inc. occupies 825 Stewart Drive.
Chlorinated volatile organic compounds (VOCs) are the major contaminants tested and found in the soil and groundwater samples (1). The highest concentration of VOCs in the soils at the TRW site were found around an underground waste solvent storage tank (1). The tank and some of the surrounding soil have been removed (1). The VOC contamination in groundwater is currently monitored by 18 monitoring wells on the former TRW property and 83 off-site wells (1). Based on monitoring data, the commingled contaminated groundwater plume (Figure 1) seems to extend as far north as Lakefair Drive, east to Santa Paula Avenue, and west to an imaginary extension of Britton Avenue (1). Remediation of the onsite-groundwater began in 1983 and off-site groundwater in 1986 (1).
Seven wells are currently extracting on-site groundwater: 3 A-zone wells, 3-B1 aquifer wells, and one B2 extraction well. The extracted groundwater is treated by an air stripping system on the former TRW property. Uncontrolled air emissions are currently regulated by BAAQMD permit for this site. After treatment, the water is released to Calabazas Creek under an NPDES permit (1). The NPDES permit requires monthly analysis of the treated water to ensure compliance with the permit discharge standards.
In addition, the AMD/Signetics/TRW Microwave have installed two off-site groundwater extraction systems. The Duane Avenue Extraction system was installed in 1986 and consists of nine wells extracting water from A, B1, B2, B3, and B4 aquifers. Alvarado Avenue Extraction System was installed in 1988 and consists of 14 wells extracting water from the B1, and B2 aquifers. Six more extraction wells were installed in 1992 (17). All extracted groundwater is transferred by a piping system to the AMD915 DeGuigne facility where the water is treated by an air-stripper followed by liquid-phase carbon absorption. About 30% of the treated water from the off-site extraction and groundwater treatment system is used as process water in current manufacturing operations at AMD 915 (1). The remainder of the treated groundwater is discharged to a storm drain tributary to Calabazas Creek.
On January 16, 1991, the staff from the CDHS ATSDR project and the project manager from the RWCQB toured the former TRW site.
The area surrounding the site is typical of light industrial zoning, with simple, pleasant landscaping, a number of 2- and 3-story buildings, surrounding asphalt parking lots, and a small amount of grassy areas with young trees and bushes. The terrain is flat. There did not appear to be any physical hazards. Potential chemical hazards around the facilities were clearly marked with Department of Transportation labels and secured behind fences or storehouses.
At the time of the site visit, groundwater remediation was occurring on company property as well as off-site. The monitoring and extraction well-heads are located just below the surface and secured with manhole coverings. Each water treatment facility is surrounded by a 12 foot-cyclone/wood slat fence and a locked gate. The back of 825 Stewart Drive, now occupied by FEI Microwave Inc., a military subcontractor, is surrounded by a 10-foot wire fence.
According to the 1980 census information (5), there are approximately 4,000 people living in the general area of the off-site groundwater contamination (Figure 1): 25% are under 18 and 5% are over 65. The racial/ethnic breakdown defined by the 1980 Census is as follows: 55%, Caucasian; 3%, black; 23%, Asian; 19%, Spanish origin (5).
The plume of contaminated groundwater extends approximately one and three-quarters mile north of the site. This area is composed of light industry and residential housing (referred to as the "San Miguel neighborhood"). The former Sunnyvale Junior High School is located west to northwest of the TRW site. The former school and surrounding sporting area are now owned and occupied by Westinghouse.
The track, softball and baseball fields and tennis courts that surround the former junior-high school are enclosed by a fence and accessible only to the Westinghouse workers for recreational purposes. Fair Oaks Park, primarily a children's playground, is located northwest of the site on the corner of Duane and Fair Oaks Avenue. To the north and northeast of the site is the newly-built AMD Submicron Development Center and the AMD 915 facility.
The closest residential neighborhood, San Miguel neighborhood, begins about 1/4 mile north of the site along Duane Avenue. According to the 1980 Census (5), of the approximately 1,500 housing units, 54% are single family homes and 24% have 10 or more units. The area consists of modest single family homes interspersed with small apartment complexes. Within 3/4 mile of the site is a mobile home park which is primarily occupied by senior citizens.
The San Miguel Child Development Center, referred to as the "San Miguel School," operates in building facilities formerly used for an elementary school. The school is located at the intersection of San Miguel Avenue and Amador Avenue and houses approximately 200 children per day. These children attend either a state child development program, a state preschool, a YMCA day-care program or a Head Start Program, all operating at the school facility. There is at least a half acre of grassy land on the side of the facility that is not included in the fenced off playground. This is apparently used as a neighborhood playground.
To the southwest of the site is a new development, Parkside Commons. This complex has total of 192 apartments located in 8 apartment buildings and a shared recreation building.
Natural Resource Use
Three major water-bearing zones (aquifers), defined as the A-, B- and C-aquifer zones, exist at the site (1). The A-aquifer is the shallowest and the C-aquifer is the deepest of these three zones (1). The B-aquifer is further defined into the B1 to B5 zones (1). The approximate depths (below ground level) at which these zones occur at the TRW 825 site are as follows: A: 10-28 ft; B1: 28-50 ft; B2: 50-70 ft; B3: 70-90 ft; B4: 90-110 ft; and B5: 110-123 ft (1). A regional aquitard, the B-C aquitard, is reportedly located at a depth range from 100-150 ft below ground level (1). The C-aquifer, which supplies most of the municipal water in the region, is located below the regional aquitard (1). A well survey of the site area indicated the presence of three wells not associated with the remediation (1). Two of these wells were identified in Santa Clara Valley Water District records as having been destroyed. The remaining well is a cathodic protection well owned by PG&E. It is unclear whether this well is operational. The only documented drinking water well located near the site is a municipal well about 2.8 miles hydraulically upgradient of the site. This well draws water from 250 feet below ground level (below the B-C regional aquitard).
The aquifer zones appear to consist of mostly discontinuous layers and lenses of fine to coarse sand, gravels, and often a substantial proportion of clay and silt (1). These predominantly discontinuous layers and lenses are separated and/or isolated by low-permeability clays and silts (aquitards).
There are no natural surface water bodies located in the vicinity of the site. However, the Santa Clara Valley Water District maintains a concrete-lined drainage channel (Sunnyvale East Drainage Channel) along the western portion of the site (1). (During present drought conditions, the ditch is dry.) The channel discharges storm water into Calabazas Creek and ultimately into San Francisco Bay (1). Calabazas Creek is located 1.2 miles east of the site. Guadalupe Slough and the salt evaporation ponds of San Francisco Bay are located approximately 2 miles north of the site.
The area around the TRW site does not appear to support significant wildlife and the agricultural land use, if any, is minor.
On January 1, 1988, the cancer reporting system (CDHS California Tumor Registry) began collecting data for the region that includes the TRW site and surrounding area. The data for 1988 was released February 18, 1991 (6).
In 1983, the CDHS California Birth Defects Monitoring Program began tracking Santa Clara County (7). These databases are further discussed in the Health Outcome Data Evaluation section of this document.
The early drafts of the public health assessment and the RWQCB March 1991 Fact Sheet (8) identified a current potential exposure pathway as inhalation of VOC vapors from the off-site groundwater plume. Since the release of this information, this exposure pathway has been a source of community concern.
Prior to the release of information about this exposure pathway, the Community Relations staff from the CDHS/ATSDR Cooperative Agreement Project spoke with the Director of the Silicon Valley Toxics Coalition, city officials from Sunnyvale, officials from the Santa Clara County Health Department, a Santa Clara County Board of Supervisors staff person, and community relations staff from the U.S. EPA and from the Department of State Toxics Substances Control. None of these individuals were aware of any recent community health concerns regarding the TRW site.
Historically, community concerns in Sunnyvale centered on groundwater and soil contamination. In the early 1980s, following the discovery of contamination at the Fairchild and IBM facilities in South San Jose, a group of environmental, labor, and other organizations concerned about groundwater contamination formed The Silicon Valley Toxics Coalition. The Coalition informed residents about the potential for extensive groundwater contamination in Santa Clara County. Consequently, the residents became better organized in expressing their health concerns.
While overseeing the cleanup of many of the Superfund sites in the South Bay, RWQCB has been the lead agency on this site In January 1990, RWQCB released their Sunnyvale Community Relations Plan incorporating into a single plan three Superfund sites (AMD 901/Signetics/TRW, AMD 915, and AMD Arques) in the City of Sunnyvale (9). This plan identified the historical community concerns in Santa Clara County as being the quality of drinking water, whether the extent of the problem had been determined, what would happen if the contamination spread, what was being done to clean up the soil and groundwater, what happened to the contaminated groundwater which was pumped out, the schedule for cleanup, and how would property values be effected.
RWQCB held a meeting with the City of Sunnyvale and ATSDR Project staff to review the draft of the March 1991 Fact Sheet. The city staff, including the Community Relations Director, the Fire Marshall, the Hazardous Materials Director, and representatives from the City Attorney's office and the Water Pollution Board, had taken considerable effort to convince the public that their drinking water was safe. The staff was concerned that the fact sheet would raise the issue of groundwater contamination again and requested that the Fact Sheet verify the safety of the municipal drinking water supply.
In mid-March, RWQCB mailed Fact sheet 2 in which they announced the Community Meeting on March 28, 1991 (8). Approximately 40 people were in attendance and they expressed concerns about the possible exposure from the off-site plume. First, there were some general questions from the attendees. Then, comments for the record were made by the Director of the Silicon Valley Toxics Coalition, the Coordinator of Children's Services for Santa Clara Office of Education, a staff person to a City Supervisor, and a resident who lived over the plume.
At the request of community members, RWQCB organized a follow-up community meeting on May 7, 1991, to more specifically address the concerns of the San Miguel School neighborhood, located over the contaminated groundwater plume. Silicon Valley Toxics Coalition publicized the meeting and about 200 people showed up. At this meeting SVTC began calling for health screening and indoor air sampling in homes. On June 17, 1991, Silicon Valley Toxics Coalition organized a forum to discuss issues related to the AMD 901/902/TRW Microwave/Signetics site (site history and clean-up measures, health concerns, and real estate concerns). A panel of community members questioned the presenters. The presenters included staff from CDHS. Again there was an interest expressed in health screening and indoor air monitoring in homes.
CDHS initiated an indoor air sampling project to investigate the possible migration of VOCs from the contaminated groundwater into buildings and homes (see Environmental Contamination Section). As part of the project, a community advisory committee was formed so that the community would understand the complexities of such a project and provide feedback and input on the methods and analysis. The advisory committee also assisted CDHS in determining the best way to share information with the community. The advisory committee decided that the best method to share the results of the indoor air sampling study with the community would be through a fact sheet. Two fact sheets were hand delivered in the San Miguel neighborhood during the course of the project (10,11).
Following are the specific issues of concern that were raised at the three community meetings:
- What is the quality of the drinking water?
- Is there a danger from eating fruits and vegetables irrigated from the water of the A-aquifer?
- What happens to the extracted water?
- If industries are filtering the contaminated water through air strippers and releasing into the air, who is monitoring this?
- What is really airborne?
- Have the hours of exposure of the children at the San Miguel School been accurately estimated in the first assessment?
- What about the exposure of the children who were attending the school before the clean-up started?
- Concerns about the sampling for VOC soil gas flux studies:
- how accurate are the sampling methods?
- how long have they been doing this sampling method?
- can weather affect the sampling?
- how many days of sampling does there need to be for an accurate picture?
- how can the RWQCB have a clean-up plan without knowing the extent of contamination?
The issue of property values was a predominant concern at the second meeting. This issue will not be addressed in the public health assessment because the focus of this document is on public health.
No community health concerns were raised during the draft health assessment public comment period. The concerns listed are discussed in the Community Concerns Evaluation section of this document.
The tables in this section list the contaminants of concern. We evaluate these contaminants in the subsequent sections of the Public Health Assessment and determine whether exposure to them has public health significance. ATSDR selects and discusses these contaminants based upon the following factors (4):
- Concentrations of contaminants on and off the site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of on-site and off-site concentrations with public health assessment comparison values for noncarcinogenic endpoints and carcinogenic endpoints.
- Community health concerns.
In the data tables that follow under the On-site Contamination subsection and the Off-site Contamination subsection, the listed contaminant does not mean that it will cause adverse health effects from exposures. Instead, the list indicates which contaminants will be evaluated further in the Public Health Assessment.
The comparison values are as follows:
| EMEG =||ATSDR's Environmental Media Evaluation Guide|
| iEMEG =||ATSDR's intermediate Environmental Media Evaluation Guide|
| CREG =||ATSDR's Cancer Risk Evaluation Guide|
| RMEG =||Reference Dose Media Evaluation Guide from U.S. EPA's Reference Dose|
| US MCL =||Maximum Contaminant Level (federal)|
| CA MCL =||Maximum Contaminant Level (California)|
Comparison values for the preliminary public health assessment are contaminant concentrations in specific media that are used to select contaminants for further evaluation. EMEGs are media-specific values developed by ATSDR to serve as an aid in selecting environmental contaminants that need to be further evaluated for potential health impacts. EMEGs are based on noncarcinogenic health endpoints and do not consider carcinogenic effects. EMEGs are derived from ATSDR's Minimal Risk Levels (MRLs). An MRL is an estimate of the daily human exposure to or dose of a chemical that is likely to be without an appreciable risk of deleterious effects (noncancer). EMEGs are typically based on chronic exposure (>365 days); however, in some cases, an IEMEG has been developed for shorter exposures (15 to 364 days).
RMEGs are similar to EMEGs in that they are used to evaluate the noncarcinogenic effects of a particular chemical. RMEGs are derived from the U.S. EPA Reference Dose (RfD). The RfD is an estimate of a daily exposure to a particular compound that is unlikely to cause adverse, noncarcinogenic health effects for a period of exposure from 7 to 70 years.
CREGs are media-specific values developed by ATSDR to serve as an aid in selecting contaminants for follow-up that are potential carcinogens. CREGs are estimated contaminant concentrations which theoretically could cause one excess cancer in a million persons exposed over a lifetime. CREGs are based on U.S. EPA cancer slope factors, which give an indication of the relative carcinogenic potency of a particular chemical.
Maximum Contaminant Levels (MCLs) represent contaminant concentrations that U.S. EPA or CDHS deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters water per day. While MCLs are regulatory concentrations, EMEGs, RMEGs, and CREGs are not.
Toxic Release Inventory
On-going facility, now occupied by FEI Microwave, Inc., and/or surrounding facilities' emissions may be contributing an additional environmental burden to the nearby population. Therefore, CDHS staff searched the Toxic Release Inventory (TRI) for the years 1987, 1988, and 1989 (the years for which TRI data is currently available). The TRI contains information on estimated annual releases (emission rates) of toxic chemicals to the environment (via air, water, soil, or underground injection). These reported releases are routine releases, spills and other accidental releases, or occasional releases from normal operation. Toxic chemical release information is submitted to the U.S. EPA by certain industries as mandated under the Emergency Planning and Community Right-to Know Act of 1986.
Although TRW is no longer occupying 825 Stewart Drive, TRI was searched by the zip code that includes this facility, which is now occupied by FEI Microwave. Fourteen facilities in the zip code area surrounding 825 Stewart Street reported the release of 507,863 pounds of chemicals, primarily volatile organic compounds and acids, into the air in 1987 (12). In 1987, these facilities reportedly released 167,750 pounds of methyl ethyl ketone, 105,050 pounds of acetone, 19,302 pounds of xylene, 10 pounds of epichlorohydrin, 9,200 pounds of 2-methoxyethanol, 7,275 pounds of glycol ethers, and 142,946 pounds of Freon 113 (12).
Eleven facilities in the zip code area surrounding 825 Stewart Drive reported the release of 256,468 pounds of chemicals, primarily volatile organic compounds and acids, into the air in 1988 (13). In 1988, these facilities reportedly released 81,179 pounds of methyl ethyl ketone, 89,027 pounds of acetone, 3,095 pounds of xylene, 11 pounds of epichlorohydrin, 6,563 pounds of 2-methoxyethanol, 1,250 pounds of glycol ethers, and 35,659 pounds of Freon 113 (13).
Eight facilities in the zip code area surrounding 825 Stewart Drive reported the release of 267,731 pounds of chemicals, primarily volatile organic compounds and acids, into the air in 1989 (14). In 1989, these facilities reportedly released 75,236 pounds of methyl ethyl ketone, 128,643 pounds of acetone, 2,726 pounds of xylene, 13 pounds of epichlorohydrin, 180 pounds of 2-methoxyethanol, 5,840 pounds of glycol ethers, 65 pounds of m-cresol, and 40,497 pounds of Freon 113 (14). Therefore, other facilities in the area influence air quality through their planned or accidental releases each year.
In 1983, the last in a series of four underground waste solvent storage tanks and associated soil were removed from the TRW site (1). Soils with total VOC concentrations as high as 15,700 parts per million (ppm) were excavated from the source area (1). Since complete excavation would have threatened the stability of the building, some of the contaminated soil still remains (1). In 1988, boring samples of the soil remaining after the excavation of the waste solvent tank near TRW 825 were analyzed for concentrations of five VOCs. Some of the borings were placed outside and some inside the building. The subsurface soil samples were taken at depths ranging from 7 to 17 ft and from the A/B aquitard at depths of 21.5 to 26 ft. Low levels of the five VOCs that were analyzed (vinyl chloride, trichloroethylene, cis-1,2-dichloroethylene, tetrachloroethylene, and 1,2-dichlorobenzenes) still remain in the soil both inside and outside the building (Table 1). The levels of these compounds do not exceed their health comparison values.
Soil samples collected near the former underground solvent waste storage tank (1988) and near the acid-neutralization system (1986) have been analyzed for total metals (Table 2). Two backyard soil borings (1989) were taken at a location remote to the point source of contamination and analyzed for total metals ("background"). Beryllium was detected in soil samples taken near the acid-neutralization tank at levels that exceeded the background sample and the health comparison value (1). Cobalt, copper, lead, nickel, and vanadium were detected in soil samples taken near the acid-neutralization tank at levels that exceeded the background sample. Because no comparison values exist for these compounds, they are considered contaminants of concern in the soil.
In 1985, soil sample borings (3-4.5 ft) from near the acid-neutralization system were analyzed for soluble metals (Table 3). None of the metals found in the soil appeared to be in a form that would migrate from the soil into the groundwater.
The vertical and horizontal extent of VOC groundwater contamination at the TRW site is characterized by 18 monitoring wells (1). The most contaminated wells are located near or downgradient (north) from the former underground tanks (1). The vertical migration of contamination is being tracked through the major water-bearing zones. The three shallowest aquifers (A, B1, and B2) are the most contaminated. Seven chlorinated VOCs were detected in the groundwater as reported in a 1990 monitoring report (15). Concentrations of trichloroethylene, 1,2-dichloroethylene, vinyl chloride, and tetrachloroethylene exceed their health comparison values and are, therefore, contaminants of concern in the on-site groundwater (Table 4).
In 1989, groundwater samples from 5 wells (3 aquifers) near 825 Stewart Drive were analyzed for metals (1). A well, located upgradient from the point source (waste solvent storage tank) and for which water analyses have shown very low concentrations of trichloroethylene and other VOCs, was sampled for background concentrations of metals (Table 5). Arsenic and nickel were detected in one well each at concentrations that exceeded their comparison values and are contaminants of concern in the on-site groundwater (Table 5).
Since 1984, AMD/Signetics/TRW Microwave (the Companies) have installed 83 monitoring wells to assess the vertical and horizontal extent of VOC migration from the AMD 901/901/Signetics/TRW 825 facilities (1). The set of extraction wells along Duane Avenue has been in operation since 1986. Another set, primarily located along Alvarado Avenue and Ahwahnee Drive, has been in operation since 1988. Nine chlorinated VOCs have been detected in the groundwater as reported in a 1990 monitoring report of selected wells (16). Concentrations of dichloromethane, chloroform, 1,1-dichloroethane, 1,1,1-trichloroethane, 1-1-dichlorethylene, trichloroethylene, 1,2-dichloroethylene, and tetrachloroethylene exceed their health comparison values (Table 6) and are contaminants of concern in the off-site groundwater.
In 1989, groundwater samples from 12 off-site extraction wells were analyzed for metals and 6 metals were detected (1). The levels of manganese detected in the off-site groundwater exceed the health comparison value, and thus, manganese is considered a contaminant of concern in the off-site groundwater (Table 7).
In order to assess the potential migration of VOCs from the groundwater into the soil column and then release to the air, the Companies sampled the flux of VOCs from the soil surface using a flux chamber (18). On March 12, 1991, the Companies sampled at five locations transecting the groundwater plume at the Westinghouse facility and the AMD and TRW properties (Figure 2). The samples were analyzed for ten target chemicals: 1,2-dichlorobenzene, 1,1-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, Freon 113, tetrachloroethylene, 1,1-trichloroethane, trichloroethylene, and vinyl chloride. Freon 113 and 1,1,1-trichloroethane were detected in most of the samples. Because these compounds were detected in the field blank, they probably arise from sources such as ambient air rather than the underlying groundwater. Isolated low levels of vinyl chloride and cis-1,2-dichloroethylene were detected at one location (#6 in Figure 2), and a low level of 1,2-dichlorobenzene was detected at another location (#5 in Figure 2).
The Companies had a second round of soil gas flux sampling performed on April 8, 1991 (18). Seven locations were sampled during this event, including locations 4 and 6 from the March 12, 1991, sampling round. The new locations (Locations 7, 8, 9, 10, and 11 in Figure 2) are on the San Miguel School property; these locations form a transect across the school property. Freon 113 and 1,1,1-trichloroethane were detected in all the samples and at a similar concentration in the field blank (Table 8). Again this seems to indicate that sources other than the underlying groundwater are responsible (i.e. ambient air). The only chemical of concern detected in the soil gas samples was trichloroethylene found at a concentration of 0.46 ppb in the sample from Location 9 (Table 8).
As a part of the final clean-up plan, the Companies have conducted off-site soil flux sampling twice a year, once in the summer, once in the winter, at the same sampling locations as the April 8, 1991, sampling (19-21). 1,1,1-Trichloroethane and Freon 113 have been generally detected in most of the samples as well as in the field blank (Table 8). Tetrachloroethylene was detected at a number of the sampling locations during the July 1991 sampling event, but the field blank also contained tetrachloroethylene at a comparable concentration. Trichloroethylene has been detected in three of the four sampling events at Location 9. Trichloroethylene has also been detected at Location 7 during the summer months and at Location 8 during the July 1992 sampling event.
The soil flux data indicate that trichloroethylene may be migrating from the soil at sampling location 9. (Sampling location #9 is in the middle of the plume). To a lesser extent, migration of trichloroethylene from soil to air may also occur during the hot summer months at sampling points 7 and 8.
In order to investigate the possible migration of VOCs from the groundwater which could be impacting the San Miguel neighborhood, the Environmental Health Investigations Branch (EHIB) within CDHS requested assistance from the Air and Industrial Hygiene Laboratory (AIHL) within CDHS (22). On February 18 and 29, 1992, AIHL conducted outdoor and indoor air sampling at San Miguel School. San Miguel School is located over the middle of the contaminated groundwater plume. AIHL also sampled inside and outside at Cherry Chase School, a school of similar construction to San Miguel School but not located over a contaminated groundwater plume. Two rooms were sampled at San Miguel School and one room at Cherry Chase School. One outdoor sample was also taken at each school.
The samples were collected by drawing a fixed rate of air through a tube filled with a material (Tenax or multisorbent) on which the organic material in the air is absorbed. In the laboratory, the organic materials are de-sorbed from the tube and identified and quantified using gas chromatography. AIHL calculated the ventilation rates inside the school rooms by measuring the dispersion of a tracer gas. AIHL also measured the pressure differences between indoors and outdoors using a micromanometer. AIHL completed their laboratory analyses in mid-June 1992 (23).
In preparation for a community meeting scheduled to take place August 8, 1992, EHIB presented the results of AIHL testing in a fact sheet distributed in the San Miguel neighborhood in early August 1992 (10). The fact sheet stated: "preliminary results of the indoor and outdoor air samples taken at San Miguel and Cherry Chase Schools indicate that VOCs are not coming up from the contaminated groundwater and accumulating inside the buildings. Outdoor air samples taken at both San Miguel and Cherry Chase Schools detected higher levels of several chemicals (trichloroethylene, 1,1-dichloroethylene, methylene chloride) than levels reported for other urban areas."
EHIB contacted the BAAQMD to notify them of these unusually high outdoor readings (24). On August 2, 1992, BAAQMD sampled outdoors at both schools. BAAQMD collected air samples using vacuum pressured stainless steel canisters with a control valve that was opened to allow a set flow of air into the canister. On August 3, BAAQMD notified EHIB that they did not detect any trichloroethylene, methylene chloride, or 1,1-dichloroethylene outdoors at either school.
On August 3, AIHL notified EHIB that during their sampling, contamination had been introduced onto the Tenax and multisolvent tubes. An apparatus used to measure the flow rate of the air through the tubes contained a solution with trichloroethylene, 1,1-dichloroethylene, and methylene chloride in it. Since the apparatus was attached at the front of the tube and not behind the tube, the samples were contaminated with trichloroethylene, 1,1-dichloroethylene, and methylene chloride.
Given BAAQMD's ability to rapidly collect and analyze air samples, EHIB then requested BAAQMD to sample indoors and outdoors at both schools. On the morning of August 4, BAAQMD sampled inside Rooms B3 and B4 at San Miguel School, outside at San Miguel School, inside Room 14 at Cherry Chase School, and outside Cherry Chase School. By late afternoon, BAAQMD reported to EHIB that trichloroethylene was detected inside San Miguel School (higher concentration in Room B4 as compared to Room B3) but not inside Cherry Chase School and not outdoors at either school (25).
On August 11th, EHIB contacted the director of the San Miguel School to inquire about recent activities in Rooms B3 and B4 that might have influenced the detection of these compounds. After investigating, the director reported that the carpet in Room B4 had been cleaned on August 3. EHIB requested and received a list of cleaning products that had been used in the carpet cleaning. EHIB contacted the manufacturers of these products who claimed that neither trichloroethylene nor 1,1,1-trichloroethane are used in making any of their products.
On August 12th, EHIB conducted a community meeting at San Miguel School and presented the AIHL and BAAQMD air sampling data. The AIHL data indicated that 1,2-dichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, and vinyl chloride were not migrating from the groundwater into San Miguel School. Tetrachloroethylene and 1,1,1-trichloroethane were detected by AIHL inside San Miguel School and inside Cherry Chase School at levels that are typical for indoor air and below a level of health concern.
The lack of good trichloroethylene data from the AIHL sampling was a major concern.
BAAQMD detected trichloroethylene inside San Miguel School, but not at a level of health concern. However, because it was not detected inside Cherry Chase School, the community requested further sampling.
BAAQMD analyzed the three cleaning solutions used for carpet cleaning in Room B4. None of the solutions contained trichloroethylene or 1,1,1-trichloroethane (26).
EHIB requested BAAQMD and AIHL to work together under EHIB's direction to resample at San Miguel and Cherry Chase Schools under a variety of ventilation situations (27). BAAQMD would sample and analyze the indoor and outdoor air. AIHL would measure the ventilation rate and depressurization of the school rooms.
On November 9, 1992, a second indoor air investigation was conducted at San Miguel and Cherry Chase Schools. Three different ventilations scenarios were studied: doors and windows closed, exhaust system turned off; doors and windows closed, exhaust turned on; doors and windows open, exhaust system turned on.
The air sampling data from November 12 were very similar to that collected in August by BAAQMD (26). No dichloroethylene or vinyl chloride was detected inside or outside either San Miguel School or Cherry Chase School (Table 9). Tetrachloroethylene, 1,1,1-trichloroethane, and benzene were detected at low concentrations inside and outside both San Miguel School and Cherry Chase School. Trichloroethylene was detected in both rooms at San Miguel School but not inside or outside at Cherry Chase School or outside at San Miguel School.
Table 10 presents the sampling data with the different ventilation conditions (24, 28). With the windows and doors closed and the ventilation off, there is substantial depressurization inside the rooms at San Miguel School (-9 Pasquals inside Room B3 and -10 Pasquals inside Room B4). Since the exhaust fans were not operating, this depressurization is probably the result of the wind forces on the building. This depressurization is the force pulling the soil gas and ambient outdoor air into the structure. When the ventilation is turned on, but the windows and doors are still sealed, the depressurization is doubled or tripled (26 Pasquals in Room B3 to -17 Pasquals in Room B4). In this scenario, there is an enhanced pull on the soil gas and the outdoor air to infiltrate into the room through cracks in the foundation or walls where the utilities penetrate the structure.
In addition to the greater pull, there is also a change in the air exchanges that occur per hour when the ventilation system is turned on (Table 10). With the room essentially static in the first sampling scenario, there is approximately 0.2 air exchanges per hour. Whereas with the ventilation system on and the windows and doors still sealed, the air exchanges increase by approximately seven-fold at San Miguel School. However, the levels present are below comparison values, so trichloroehtylene is not a contaminants of concern in the air.
ATSDR presumes that site investigation protocols and analytical data have been reviewed and accepted by the agencies for which the work is being performed. The data used in the preparation of this public health assessment have been reviewed and qualified appropriately. The completeness and reliability of relevant reference information determines the validity of the conclusions drawn in this Health Assessment.
There are no physical hazards at the site.
Chlorinated VOCs transported off-site by groundwater volatilize and diffuse through the subsurface and surface soils, ultimately being released to the ambient air or creeping into confined spaces such as homes or other buildings. An indoor air study (see Public Health Implications section and Appendices C and D) indicates that people have been exposed to low levels of VOCs migrating from the site into indoor air at San Miguel School. Exposure to the VOCs is primarily through inhalation. Some dermal absorption may occur. The number of people exposed is not known; however, up to 4,000 people living in the area near the site have possibly been exposed to very low levels of the contaminants at some time.
Most of the detected soil contamination associated with the primary point sources of contamination has been removed from the site. The remaining contaminated subsurface soils are located beneath 825 Stewart Drive and are not accessible to people. Therefore, no exposures are likely to occur.
The concentrations of certain VOCs and metals in on-site groundwater are greater than their corresponding health comparison value. However, there are no wells located on-site except for monitoring or extraction wells.
The concentrations of certain VOCs and manganese in the off-site groundwater are greater than their corresponding health comparison value. A well survey of the site area indicated the presence of three wells not associated with the remediation (1). Two of these wells were identified in Santa Clara Valley Water District records as having been destroyed. The remaining well is a cathodic protection well owned by PG&E. It is unclear whether this well is operational. The only documented drinking water well located near the site is a municipal well about 2.8 miles hydraulically upgradient of the site. This well draws water from 250 feet below ground level (below the B-C regional aquitard).
Thus, there are currently no private or municipal wells in the impacted area and the likelihood of a well being placed within the confines of the contaminant plume is low. At this time, sufficient water for municipal use is available from aquifers having higher quality water and water yield. Additionally, regulatory barriers prohibiting installation of shallow private wells are in effect. Therefore, no exposures are expected to occur through use of contaminated groundwater.
Several factors determine whether harmful effects will occur after exposure to a particular contaminant and the type and severity of those health effect. These factors include the dose (how much), the duration (how long), the route by which people are exposed (breathing, eating, drinking, or skin contact), the other contaminants to which they may be exposed, and their individual characteristics such as age, sex, nutrition, family traits, life style, and state of health. The scientific discipline that evaluates these factors and the potential for a chemical exposure to adversely impact health is called toxicology.
As discussed above, residents living in the area north of the site and above the plume of contaminated groundwater may be exposed through inhalation of chlorinated VOCs volatilizing from shallow groundwater. In the Baseline Public Health Evaluation, the potential exposure to VOCs volatizing from the contaminated groundwater and accumulating within buildings was evaluated. A theoretical indoor-air model was used to estimate the air concentrations within single-family residences located north of Duane Avenue and within San Miguel School (2). This indoor air concentration was then used in a quantitative risk assessment.
The theoretical indoor air model used for the quantitative risk assessment resulted in the following evaluation. The lifetime excess cancer risk caused by the inhalation of volatilizing VOCs from the shallow groundwater for off-site residents, assuming all levels in groundwater would migrate into the home, were 1 x 10-4 (low increased risk) for average case conditions, and 2 x 10-3 (moderate increased risk) for plausible maximum conditions. Upperbound lifetime excess cancer risk for children attending San Miguel School facility programs were 4 x 10-8 (no increased risk) for average case conditions and 6 x 10-7 (no increased risk) for plausible maximum conditions. For comparison, U.S. EPA considers an excess cancer risk of 1 in 10,000 (1 x 10-4) to 1 in 1,000,000 (1 x 10-6) as appropriate clean-up goals. The majority of risk in all cases was due primarily to 1,1-dichloroethylene, listed as a possible carcinogen (Group C) by the U.S. EPA.
To test the model and to determine actual levels of air contamination that people were inhaling, the Companies chose to investigate this pathway by monitoring soil vapor emissions using a U.S. EPA approved flux chamber method (16-20). Low levels of trichloroethylene, 1,1,1-trichloroethane, Freon 113, cis-1,2-dichloroethylene, and tetrachloroethylene were found in preliminary soil vapor emission analysis off-site of TRW (Table 8).
However, indoor air studies suggests that soil vapor flux measurements may not be appropriate for assessing indoor exposure. A typical house is a negative pressure zone and thus it literally draws vapors from the soil (29). The soil vapor flux was measured using an isolated flux chamber and this device imparts a neutral pressure over the soil.
To further explore this potential pathway, EHIB proposed sampling of indoor air at the San Miguel School which lies over the middle of the contaminated groundwater plume. An advisory committee, composed of community members and government representatives, met with EHIB to oversee the indoor air study. The committee has provided ongoing consultation regarding the purpose of the study, study design, and study result interpretation (for details see Appendices C and D). To evaluate possible health effects from chemicals found inside San Miguel School, an action level table was developed (Table 10).
BAAQMD conducted indoor and outdoor air sampling at San Miguel School and Cherry Chase School on November 9, 1992. The results of the BAAQMD sampling showed that three site-associated chemicals (trichloroethylene, tetrachloroethylene, and 1,1,1-trichloroethane) were detected at low levels inside San Miguel School. Because of the way the study was conducted, it was possible to distinguish that the primary sources for tetrachloroethylene and 1,1,1-trichloroethane were commercial products and building materials inside the classrooms (for details see Appendix D). Contaminated groundwater was identified as the primary source of trichloroethylene inside San Miguel School.
None of the study chemicals were detected at a level of public health significance, and all of them were detected at levels considered typical for indoor air (Level 1 in Table 10). Health effects have been reported for people who are exposed, usually in the workplace, to much higher levels of some of the VOCs than what has been found in the neighborhood around the TRW site. However, contaminant levels in groundwater that may migrate to indoor and outdoor air are expected to decrease over time because of the groundwater treatment system that is in place. Because the levels are expected to decrease rather than increase, no further evaluation of the individual contaminants is presented.
Cancer Tumor Registry
Information is available from California's tumor registry for 1988. For 1988, there were a total of 58 cases coded to the three census tracts partly contained within the contaminated groundwater plume (33). The five most common cancers in the general population are lung, breast, colorectal, prostate, and bladder; these are also the most common cases among these census tracts. Thus, the cancer cases in the population around the site reflects what is seen in cancer cases in the general population.
Birth Defects Registry
Information is available from California's birth defects registry for 1983 to 1990. Nothing in the literature was found to indicate that adverse health outcomes would be expected as a result of the identified exposures to VOCs from the site. Therefore, this database has not been evaluated (34).
We have addressed each of the community concerns about health as follows:
- What is the quality of the drinking water?
- Is there a danger from eating fruits and vegetables irrigated from the water of the A-aquifer?
- What happens to the extracted water?
- If industries are filtering the contaminated water through air strippers and releasing into the air, who is monitoring this?
- What is really airborne?
- Have the hours of exposure of the children at the San Miguel School site been accurately estimated in the risk assessment?
- What about the exposure of the children who were attending the school before the clean-up started?
- There were several questions about the sampling for VOC soil gas flux studies:
- How accurate are the sampling methods?
- How long have they been doing this sampling method?
- Can the weather effect sampling?
- How many days of sampling does there need to be for an accurate picture?
- Will there be indoor air testing in San Miguel School? In my home?
- Will the Cancer and Birth Defects Registries be checked to see if there is a correlation between registry data and exposure to contaminants?
- What is the plan for a medical survey/health effects study?
All drinking water must meet state and federal drinking water criteria. The drinking water serving the neighborhoods surrounding the TRW site is serviced by the Sunnyvale Municipal Water, which must monitor the water supply regularly to ensure its safety.
No. The chemicals of concern are volatile chemicals. As plants go through the evapotranspiration, they would release the majority of these chemicals into the air (35). They would not become concentrated in the fruits or vegetables.
The treated water from the on-site groundwater treatment system is discharged under NPDES permit to Calbazas Creek. The extracted water from the off-site area is treated in the water treatment systems near the AMD 915 facility and the treated water is used in the manufacturing process at AMD 915 or landscaping or released to a storm drain tributary to Calabazas Creek under NPDES permit.
BAAQMD is charged with permitting the air strippers.
The BAAQMD has been contacted by RWQCB to address this question. RWQCB will set a mechanism to keep the community informed of what is found.
There are some limitations to the model that was used. The assumption was that the children were in school for 4 hours per day, 250 days per year, for 2 years or 8 hours per day, 250 days per year for 4 years. The fact that the children could be both residents in the area surrounding the site and also attend the school was not taken into account.
It is impossible to predict where the plume was at that point. The plume began at the source, and it has taken years for it to get to where it is now. The problem at the time was probably the same magnitude that it is now or even less.
There is a 75% accuracy rate in this sampling method. The detection limit is in the low parts per billion.
This method for soil vapor analysis has been approved by the U.S. EPA for several years.
Yes. The first sample was taken during a period of cold and rainy weather. It has been repeated several times on hot, dry days. This provided more opportunity to capture the vapors.
As directed in the clean-up plan, the Companies have conducted flux
chamber measurements twice a year for the last two years (29). The need for
this monitoring is being reevaluated by U.S. EPA and RWQCB.
Yes. An indoor air sampling study was carried out at San Miguel School. This study was designed to evaluate if levels of VOCs found in San Miguel School were higher than the low levels of VOCs commonly found in most buildings. These low levels of VOCs (called background levels) are primarily due to the use of such products as building materials, cleaning solvents, and heating fuels. (For further information about the indoor air sampling at San Miguel, see the Environmental Pathways section and Appendices C and D).
The results of the indoor air sampling study indicate that the levels of chemicals found inside San Miguel School are considered typical for indoor air based on studies of indoor air quality done throughout the United States and Europe. Chemicals found at these low levels are not expected to cause health problems. CDHS and the Advisory Committee believe San Miguel School was the best location for evaluating the potential impacts of VOCs on the San Miguel neighborhood. Since the level of VOCs are below health concern, sampling of indoor air is not planned for individual homes.
No. The low level of chemical exposure that might arise from this site's contamination does not warrant further evaluation of that data.
At present there are no plans for such a study.